ADORA2A and COVID-19: However, apart from three reports describing that inhaled adenosine seems beneficial in patients with COVID-19-pneumonia [35], that an A2AR agonist regadenoson reduces inflammatory burden in 5 COVID-19 patients [36], that P2X7R controls the replication of the alpha SARS-CoV-2 variants [37] and that soluble P2X7R is increased in the plasma of COVID-19 patients [38], there is scarce experimental evidence linking P2X7R or A2AR to the severity of COVID-19.